In recent years, wireless power supply systems that supply power wirelessly to a battery mounted in a moving body such as a vehicle have been proposed. The wireless power supply systems are provided, for example, with a power-receiving coil mounted in the moving body and a power-supplying coil installed on the power supply side, and transmit electric power using a magnetic field that is formed by the power-supplying coil.
In the wireless power supply systems, it is known that if a foreign matter that is formed wholly or partly from an electrically conductive material such as metal or conductive plastic (i.e., a conductive foreign matter) intrudes between the power-receiving coil and the power-supplying coil, then a loss in energy occurs due to the heat generated by the conductive foreign matter, and there is a decrease in the transmission efficiency. To deal with this problem, for example, as is shown in Patent document 1, it has been proposed that countermeasures be devised that prevent a foreign matter from intruding between the power-receiving coil and the power-supplying coil.